1. Field of the Invention
The present invention relates to a manufacturing apparatus having a film formation system for depositing materials which can be deposited by vapor deposition (hereinafter, an evaporation material), a light emitting device which has an organic compound layer as a light emitting layer and for which the manufacturing apparatus is used, and a manufacturing method thereof. Specifically, the invention relates to a manufacturing apparatus and a film formation method (a vapor deposition method) for forming a film by vaporizing an evaporation material from a plurality of evaporation sources disposed to be opposite to a substrate.
2. Description of the Related Art
In recent years, research related to a light emitting device having an EL element as a self-luminous light emitting element has been advanced. The light emitting device is referred to as an organic EL display or an organic light emitting diode. Since these light emitting devices have characteristics such as a fast response suitable for movie display, low voltage, low power consumption driving, or the like, they attracts an attention for a next generation display including new generation's cellular phones and portable information terminals (PDA).
An EL element having an organic compound layer as a light emitting layer has a structure in which an organic compound layer (hereinafter, referred to as an EL layer) is sandwiched between an anode and a cathode. Electro luminescence is generated in the EL layer by applying an electronic field to the anode and the cathode. Luminescence obtained from the EL device includes luminescence generated in returning to a base state from a singlet excited state (fluorescence) and luminescence generated in returning to a base state from a triplet excited state (phosphorescence).
The EL layer has a laminated structure typified “a hole transporting layer, a light emitting layer and an electron transporting layer”. EL materials for forming an EL layer are classified broadly into low-molecular (monomer) materials and high-molecular (polymer) materials. The low-molecular materials are deposited using a vapor deposition system.
A conventional vapor deposition apparatus has a substrate holder where a substrate is set, a crucible encapsulating an EL material, that is an evaporation material, a shutter to prevent the EL material to be sublimed from rising, and a heater for beating the EL material in a crucible. Then, the EL material heated by the heater is sublimed and deposited on a rolling substrate. At this time, in order to deposit uniformly, the distance between the substrate and the crucible need to be 1 m or more.
According to a conventional vapor deposition apparatus and a conventional vapor deposition method, when an EL layer is formed by vapor deposition, almost all the sublimed EL material is adhered to an inner wall, a shutter or an adherence preventive shield (a protective plate for preventing an evaporation material from adhering to an inner wall of a film formation chamber) at inside of the film formation chamber of the vapor deposition system. Therefore, in forming the EL layer, an efficiency of utilizing the expensive EL materials is extremely low i.e. about 1% or less and manufacturing cost of a light emitting device becomes very high.
According to a conventional vapor deposition system, in order to provide a film with uniform thickness, it is necessary to separate a substrate from an evaporation source 1 m or more. Therefore, the vapor deposition apparatus grows in size, a period required for exhausting each film formation chamber of the vapor deposition apparatus is prolonged; therefore, film formation speed is slowed down and throughput is lowered. Also, in using a large substrate, the film thickness between a center portion and a marginal portion of a substrate easily becomes uneven. Further, the vapor deposition apparatus has a structure for rotating a substrate; therefore, there is a limit in the vapor deposition apparatus which handles a large substrate.
In view of the above-described problems, the present inventors have proposed a vapor deposition apparatus (Reference 1. Japanese Patent Laid-Open No. 2001-247959 and Reference 2. Japanese Patent Laid-Open No. 2002-60926).